The present invention relates generally to pianos, and more particularly to an improvement in pianos for preventing a tensioned string from quickly and violently bounding when the string snaps, i.e. breaks.
As well known, acoustic pianos have a plurality of tensioned or stretched strings. Grand pianos, for example, generally include about 230 strings stretched under tension, of which the strings for a bass range are each in the form of a single steel core wire with a copper wire wound thereon (i.e., in the form of a “wound wire”) while the strings for mid and treble ranges are each in the form of a core wire with no winding wire (i.e., in the form of an “unwound wire”). These strings are stretched over a frame (iron board), constituting an overall framework of the body of the grand piano, under uniform tension (e.g., about 90 kg) generally in a direction from the front (i.e. keyboard side) toward the rear (i.e., in a front-to-rear direction) of the piano. For efficient arrangement of the over-200 strings within the piano body, the strings for the bass range are positioned over and obliquely across the other strings (i.e., strings for the mid and treble ranges); namely, the strings (wound wires) for the bass range are positioned at a higher level than the other strings.
Mounting structure per string is briefed below. The string has a rear end portion caught or engaged by a projecting pin provided on a rear frame section, and a front end portion wound on a tuning pin provided on a front frame portion (so-called “pin plate”). As also well known, the piano is tuned by the respective tuning pins of the strings being turned with a tuning hammer. FIG. 4 is a schematic sectional view taken along a front-and-rear direction of the piano, which extractively shows how the rear end portion of the string is fixed in place on the frame. In FIG. 4, reference numeral 1 represents a side plate forming a rear side surface of the piano body, and 2 represents a soundboard. Frame pin 4 is provided on and projects upwardly from the upper surface of the frame 3. The string (wound wire in the illustrated example) 5 has an engaging ring formed or provided on its rear end for engagement with the frame pin 4. Namely, the string 5 is fixed at the rear end by the frame pin 4; that is, the rear-end engaging ring is engaged around and held by the frame pin 4. By winding up the front end portion of the string 5 on the tuning pin with the rear end portion (i.e., engaging ring) engaged by the frame pin 4, the string 5 is imparted with a tensile force or tension in the front-and-rear direction of the piano. As shown, the frame pin 4 supporting the rear end portion of the string 5 on the frame 3 is slightly inclined toward the rear of the piano, allowing for the tension imparted to the string 5.
However, the piano string 5 may snap, i.e. break, due to aging, rust, excessive tension imparted thereto, etc. Typically, the string 5 tends to snap or break at or around a point thereof hit by a corresponding hammer, i.e. near its front end. As noted above, a great tensile force normally acts on the stretched string 5 in the front-and-rear direction, and the string 5 is kept in the stretched or tensioned state merely with the rear-end engaging ring engaged around the frame pin 4 that is slightly inclined rearward. Thus, in case the string 5 breaks at a point near its front end, the portion of the string 5 located rearward of the broken point would be quickly tugged with a great force toward the rear of the piano, as a reaction resulting from a sudden loss of the so-far imparted tension. In such a case, the engaging ring of the string 5 may easily slip out of the engagement with (i.e., disengage from) the frame pin 4 and bound (leap) quickly and violently away from the initially-stretched position, sometimes even beyond the rear side plate 1 or outside the piano. The thus-bounding broken string 5 often hits outer covering members of the piano, such as the rear side plate 1 and roof plate, with a very strong force, thereby damaging the outer covering members. Particularly, if the broken string 5 is a wound wire of the bass range located at a higher level, the string 5 is more likely to damage the rear side plate, roof plate, etc. because there is provided no particular member for preventing the violent bounding of the broken string 5. Further, because the grand piano is often used with the roof plate kept in its raised or open position and thus the interior of the instrument body exposed to the outside, even external flaws thus caused in the inner surfaces of the rear side plate, roof plate, etc. are undesirable in that they aesthetically impair the appearance of the grand piano. Furthermore, because the outer covering members, such as the rear side plate and roof plate, are not readily replaceable, it is also desirable to prevent damages to these members as effectively as possible.